Electromagnetic switch



F. BAUER ETAL ELECTROMAGNETIC SWITCH AFiled sept. a, 1967 May 14, 1968 F. BAUER ETAL 3,383,634

ELECTROMAGNET I C SWITCH Filed Sept. 8, 1967 2 Sheets-Sheet 2 fxeem United States Patent O 3,383,634 ELECTRGMAGNETIC SWITCH Franz Bauer and Karl Preissler, Vienna, Austria, as-

signors to Hubert Laurenz Naimer, Vienna, Austria Continuation-impart of application Ser. No. 453,962,

May 7, 1965. This application Sept. 8, 1967, Ser.

Claims priority, application Austria, .lune 3, 1964,

A 4,787/64 2 Claims. (Cl. 335-124) ABSTRACT F THE DISCLOSURE An electromagnetic switch whose core and armature have opposite pole faces in the passage of the magnetic Winding in which they are axially movable, the winding, armature, and core being enveloped in plastic except for the pole faces, and the clearance between the slidably engaged axial plastic surfaces permitting tilting movement of core and armature for full area contact between the pole faces. A lever pivoted on the switch housing is engaged by stub shafts on the armature envelope with sufficient clearance for rectilinear axial armature movement during the contact-opening or closing angular movement of the lever.

Cross references to related application This application is a continuation-in-part of our copending application Ser. No. 453,962, led on May 7, 1965.

Background of the invention This invention relates to electromagnetically operated switches, and particularly to an improvement in the apparatus disclosed and claimed in the afore-cited patent.

While the switch disclosed in the earlier patent has been manufactured and used successfully, there has been a need for an even simpler switch which has a long useful life but can be mass produced at low cost. Operation of a switch over an extended period without repair to its mechanical parts was available heretofore only if the parts were made to exacting specifications, assembled by skilled personnel, and often also adjusted after assembly. These conditions cannot be met economically in mass production.

The object of the instant invention is the provision of a switch of the general type disclosed in the afore-cited patent whose mechanical elements may largely consist of an injection-molded thermoplastic resin composition with the usual generous tolerances required for such moldings, and yet not subject to the rapid wear which is caused in known switches by misalignment of low precision parts.

Summary of the invention The magnetic circuit in the switch of this invention includes a core member and an armature member which are in part axially slidably received in a passage of the magnet winding and having opposite pole faces in the passage. The winding has an envelope of a resilient synthetic resin composition, such as nylon, which covers the passage wall, and similar envelopes cover the axial walls of the core and armature members in the passage but leave the pole faces exposed. The envelopes of the core and armature members slidably engage the envelope of the winding with sufficient clearance transversely of the axis for guiding axial movement of the associated members while permitting limited tilting movement of the same transversely of the axis.

The armature member is connected tothe movable contacts of the switch by a lever pivotally mounted on the switch housing, a pivot connecting the lever to the armature member with sufficient clearance to permit rectilinear axial movement of the armature member in the winding passage while the contacts are moved between the circuit opening and circuit closing position by the necessary angular movement of the lever relative to the housing. Resilient abutments are provided to limit the axial movement of the core member to a distance which is greater than the transverse clearance mentioned above, but is only a small fraction of the greatest transverse dimension of the passage in the magnet winding.

Other features, additional objects and many of the attendant advantages of this invention will be readily appreciated as the same is better understood by reference to the following detailed description of a preferred embodiment when considered in connection with the accompanying drawing.

Brief description of the drawing In the drawing:

FIGURE 1 shows a magnetic switch of the invention in side elevational section on the line I-I in FIGURE 2;

FIGURE 2 is a front-elevational view of the switch of FIGURE l in section on the line II-II, the contact arrangement having been omitted; and

FIGURE 3 shows the apparatus of FIGURE 1 without the top part of its housing and associated magnets in plan view.

Description ofthe preferred embodiment Referring now to the drawing in detail, and initially to FIGS. 1 and 2, there is seen an electromagnetically operated switch whose housing 1 accommodates four identical fixed Contact assemblies 2. Only one contact assembly 2 is shown in detail in FIG. 1. FIG. 2 diagrammatically illustrates the side-by-side arrangement of the assemblies on the base plate 12 of the housing 1.

Two parallel, horizontal guide grooves 13 in the plate 12 are engaged by conforming projections 14 on contact carriers 15, two carriers 15 being provided in each assembly 2 and spaced transversely of the grooves 13. A binding post 16 on each carrier 15 is connected by a sheet metal strip 17 to a fixed contact 18 on the carrier near the other carrier 15. The associated movable contacts 19 which connect the contacts 18 when the switch is closed are mounted on a flat metal bar 20 which is vertically guided in one of four openings 21 of a slide 22, and is normally urged against the bottom wall of the opening by helical compression springs 24 interposed between the bar 20 and the slide 22. The drawing shows only one of the openings 21 and the associated movable contact assembly, the others being identical with the illustrated structure.

The slIde 22 is attached to the center portion 33 of a U-shaped frame 32 whose vertically extending legs are recessed at their ends so as to be 'hook-shaped in section, as seen in FIG. 2. The frame 32 is slidably received in a groove 3@ which extends over the bottom plate 12 and the side walls of the housing 1.

Except for the conductive elements and springs mentioned, the structure described so far consists entirely of plastics, preferably nylon. The front and back of the housing 1 are generally open, and the side walls are connected above the contacts 18, 19 by transverse reinforcing bars 40, 42 in which metallic tie rods 43 are embedded.

An upper housing part 50 having the shape of an upwardly open box rests on the transverse bar 40 to which it is xedly attached. The housing part 50 has a dat, horizontal bottom wall 51, side walls 52, and a front wall 53. It is rearwardly partly open, as is best seen in FIG. 3. Two elongated troughs 54 extend along the tops of the side walls 52 with which they are integral. The longitudinal end walls 55 of the troughs 54 have slots 55', 55",

3 and the troughs are bounded on one longitudinal side by the side walls 54' of the housing 1.

Each trough 54 accommodates a helical compression spring 56 between a fixed tubular abutment 59 and an abutment shoulder on a pin 58 which is coaxial with the spring 56 and guided in the bore of the abutment 59 and in the slots 55', 55". The pin 58 is normally held in the position seen in FIG. 3 by the spring 56, and projects outward of the associated trough 54.

The box-shaped housing part t) accommodates the magnet assembly 60 of the switch. Each of two windings 62 of the assembly 60 has the shape of a ring about a horizontal axis in which corresponding parts of the armature 64 and of the core 65 are axially guided, as will presently be described in more detail.

The armature is pivotally fastened to one arm 66 of a broad rocker 67 mounted between the side walls of the housing 1 on the pivot pin 64. The other arm 68 of the rocker 67 extends above the top of the slide 22, and the lateral edges 68 of its free end loosely conform to the hook-shaped leg ends of the frame 32 with which they are interchanged. The spring-loaded pins 56 engage the rocker arm 66 and normally hold the rocker 67 in the illustrated position in which the armature 64 is separated from the core 65 by a wide gap 70.

The armature 64 consists of laminated ferrous material, as is conventional, the pack of metal sheets being partly embedded in a nylon envelope 72. Stub shafts 73 integral with the envelope 72 coaxially project from the same into loosely fitting openings in the rocker arm 68, not themselves visible in the drawing. The metal sheets of the armature have approximately aligned openings filled with a rod 74 of the plastic envelope during the same injection molding operation in which the envelope 72 and the stub shafts 73 are formed.

The core 65 mainly consists of laminar ferrous metal embedded in a plastic envelope 75 from which the pole faces of the core project toward the exposed pole faces on the armature 64. The same plastic material, preferably nylon, forms a rod 76 which holds the core laminations to each other as described with reference to the rod 74. An abutment pin 77 integrally projects from each side of the plastic core envelope 75 for cooperation with a corresponding arm 80 which upwardly projects from the bottom wall 51 of the housing part 50 with which it is integrally molded of nylon. The dimensions of each arm 80 are selected to give it the characteristics of a sti spring.

The windings 62 are also embedded in a nylon shell 75 which lines the guide passages for the armature 64 and the core 65. Each winding 62 is secured against excessive movement along the passage axes by projections 82, 83 on the hollow cover 90 of the housing 1, and a similar projection 85 on the front wail 53 of the housing part 50 limits movement of the core 65 to a clearance a between the projection and the core of about 0.2-0.4 mm. in a direction away from the armature 64, and a clearance b between the core and the arm 80 of about 0.5 mm. in a direction toward the armature. The transverse clearance of the core in the passages of the windings 62 is about 0.1 to 0.5 mm. The transverse clearance of the windings 62 in the switch housing is practically zero.

The armature 64 is received in the guide passages of the windings 62 with a transverse clearance of 0.1-0.3 mm., and the clearance between the stub shafts 73 and the housing part 50 may be 0.1-0.4 mm. It is sufficient to permit rectilinear axial movement of the armature during the angular movement necessary to shift the contacts 19 between the circuit opening and the circuit closing position.

The cover 90 accommodates the switch for a pilot lamp, not shown, which indicates whether the switch is opened or closed, only the actuating member 91 of the auxiliary switch being shown in engagement with a lug 92 on the rocker arm 66 under the pressure of a non-illustrated .4 biasing spring. The arm 66 is formed with an opening aligned with the armature 64 for assembly purposes which is normally closed by a plug 93. The several parts of the housing, all of which consist of nylon or other thermoplastic material, are fastened to each other adhesively or otherwise.

The afore-described apparatus operates as follows:

When the windings 62 are energized through non-illustrated conventional terminals, the armature 64 moves toward the left, as viewed in FIG. 1, while the core 65 simultaneously moves toward the right as far as permitted by the very slight resilient deformation of the arms 80. The path of the core is greater than the transverse clearance of the armature and the core in the passage of the winding 62, considering the nylon envelopes '72, 75, but is still only a small fraction of the greatest transverse dimension of the passage.

The pole faces of the armature and of the core are made flat by stacking the laminations against a flat wall of the mold in which the laminations are assembled with each other and provided with an envelope by injection molding. As the core and the armature abuttingly engage each other, any initial deviation of their pole faces from parallel alignment is quickly remedied by a pivotal movement of either or both within the loosely confining passages in the windings 62. The magnetic force is never concentrated for a significant length of time on small pole face elements but the contact pressure is uniformly distributed over each pole face when the gap 70 is closed. It will be appreciated that the core 65 is formed with a gap (not shown) necessary to reduce the remanence in the magnetic circuit.

When the armature 64 is attracted toward the core 65, the rocker 67 is swung counterclockwise against the restraint of the springs 56, and its arm 68 depresses the slide 22 to close the circuit between the cont-acts 18, 19 under the pressure of the springs 24. The springs 56 restore the illustrated condition of the switch when the energizing current is shut off. The normally open contact arrangement of the illustrated may be replaced by a normally closed arrangement is an obvious manner, the details of the contact arrangement being known and not at the core of this invention.

The relatively stiff arms absorb the initial impact of the core 65 until the core is engaged by the moving armature 64 and moves jointly with the latter against the projection of resilient plastic. The rebound of the movable elements from the resilient plastic material of the projection 85 and of the arms 80 causes brief oscillations which are quickly damped by internal friction in this material and in the plastic envelope 75 of the core 65. Even if the windings 62 are energized by alternating current which causes cyclic variations in the magnetic attraction of the core 65 and the armature 64, the oscillatory movement of the core with the armature is damped quickly enough to prevent the separation of the pole faces which maintain engagement over their entire surface. T-here is no chattering.

The long useful life of the magnetic switches of the invention is due in part to yabsence of chattering between metallic parts which abuttingly engage each other during operation of t-he switch, and partly by the provision of plastic coatings or envelopes on the surfaces of the magnet assembly which slidingly engage each other under. Although these envelopes operate normally at somewhat elevated temperatures, significant wear has not been observed on the frictionally engaged sliding surfaces.

The dimensions of the plastic elements of the aforedescribed magnetic switch are not critical, and the clearances indicated above by way of example need not be maintained with any precision. The switch is readily assembled from relatively few parts which are fastened to each other by engagement of mating projections and recesses, or by other conventional means well within the skill of untrained personnel. The assembled switch does not require adjustment prior to being installed. The switch is thus assembled at low cost from materials which may be very inexpensive, with the possible exception of the contacts i8, 19. The switch is practically immune to the deteriorating influence of air and of airborne corrosive materials, and is not atfected by changes in ambient relative humidity which may cause the plastic parts to underH go dimensional changes.

The contacts l, 19 are engaged when the magnet windings 62 are energized, and they remain engaged until the windings are deenergized. There being no chat tering between the armature `64 and the core e5, an important cause of arcing at the contacts is eliminated, and the life of the contacts is greatly extended.

While, at this time, nylon is the preferred material of construction for all elements of the switch assembly,

`other than springs, which need not be electrically conductive or ferromagnetic, it is evident that other syn thetic resin compositions maybe employed, thermoplastic materials generally being preferred.

It should be understood, therefore, that the foregoing disclosure relates only to a preferred embodiment of the invention, and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purpose of the disclosure which do not constitute departures from the spirit and scope of the invention set forth in the appended claims.

What is claimed is:

1. In an electromagnetically operated switch assembly having a housing, a magnet winding mounted in said housing, said winding defining a passage having an axis, a magnetic circuit including a core member of ferromagnetic material having a flat poie face extending transversely of said axis, a portion of said core member being received in said passage, and an armature member of ferromagnetic material having a flat pole face opposite the pole face of said core member, a contact assembly movable between a circuit closing and a circuit opening position, and motion transmitting means operatively interposed between said armature member and said contact assembly for moving the latter between said positions thereof in response to movement of said armtaure member toward and away from the pole face of the core member, the lmotion transmitting means including a lever member pivotaily mounted on said housing, and said contact assembly moving ti from one to the other of said positions in response to a predetermined angular movement of said lever member, the improvement which comprises:

(a) an envelope of resilient synthetic resin composition covering said winding in said passage thereof,

(l) respective portions of said core member and of said armature member including said pole faces being received in said passage, and other portions of said members being outside said passage (2) said portions having axial walls in said passage;

(b) an envelope of thermoplastic synthetic resin composition on each of said axial Walls, `but leaving said pole faces exposed,

( l) the envelopes of said core member and of said armature member slidably engaging said envelope of said winding with suiicient clearance transversely of said axis for guiding axial movement of the associated members while permitting limited tilting movement of the same transversely of said axis;

(e) pivot means connecting said lever member and said armature member with suicient clearance to permit rectilinear axial movement of said armature mem-ber in said passage while said contact assembly is moved between said positions thereof by said predetermined angular movement of the lever member; and

(d) resilient abutment means limiting the axial movement of said core member in said passage.

2. in an assembly as set forth in claim 1, said abutment limiting said axial movement to a distance greater than said clearance transversely of said axis, but only a small fraction of the greatest dimension of said passage transverse of said axis.

References Cited UNITED STATES PATENTS 8/1929 Gofr 335-128 5/1966 Lawrence 335-261 

